Multi-layer lead frame for a semiconductor device

ABSTRACT

A multilayer lead frame for decoupling a power supply to a semiconductor die includes overlaying first and second lead frame bodies having an insulator disposed therebetween and at least one main lead finger extending from each body. The bodies act as a capacitor to decouple the power supply to the die. One of the bodies and respective finger provides one of power supply and ground connections for wire bonding with the die, and the other of the bodies provides the other of power supply and ground connections for wire bonding with the die. The first body includes a die paddle for supporting the die, and the second body includes a plate for overlaying the paddle with the insulator disposed between the paddle and plate, thereby providing an electrical decoupling effect therebetween upon supplying power and ground connections, respectively.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 09/633,415,filed Aug. 7, 2000, now U.S. Pat. No. 6,307,255 B1, issued Oct. 23,2001, which is a continuation of application Ser. No. 09/371,681, filedAug. 10, 1999, now U.S. Pat. No. 6,124,630, issued Sep. 26, 2000, whichis a continuation of application Ser. No. 09/002,161, filed Dec. 31,1997, now U.S. Pat. No. 5,965,936, issued Oct. 12, 1999, which is acontinuation of application Ser. No. 08/811,343, filed Mar. 4, 1997, nowU.S. Pat. No. 5,734,198, issued Mar. 31, 1998, which is a continuationof application Ser. No. 08/711,668, filed Sep. 4, 1996, abandoned.

BACKGROUND OF THE INVENTION

Field of the Invention: This invention relates in general to asemiconductor lead package system and, more particularly, to amultilayer lead frame for decoupling the power supply to an integratedcircuit chip.

State of the Art: A semiconductor integrated circuit (IC) packageddevice (part) generally includes an IC chip (die) being connected toinner leads of a lead frame by wire bonds. The chip, wire bonds, andinner leads are completely encapsulated for protection with a substance,such as plastic. Outer leads communicate with the inner leads of thelead frame, but the outer leads typically remain exposed for mounting ofthe packaged device to external circuitry, such as a printed circuitboard.

In a conventional IC packaged device, a semiconductor die is placed onand bonded to a center die paddle of a lead frame for support. Innerlead fingers of the lead frame are disposed proximate to the paddle butdo not contact or communicate with the paddle. Rather, wire bondscommunicate between contact pads (terminals) on the die and the innerlead fingers of the lead frame by spanning the gap between the die andthe fingers. The wire bonds allow for the transmission of the electricalsignals between the die and the lead frame.

The recent production of three (3) volt IC chips has created the needfor better power supply stability when testing and using the parts.Small spikes, glitches, bounces, noise, or the like (collectively“distortions”) on the power supply are more likely to cause failure inthese 3-volt parts than in five (5) volt parts which have a bettermargin of error for power supply distortions. Namely, a given distortionat 3 volts is a higher percentage of the overall voltage than that at 5volts.

In an effort to resolve potential failure from voltage distortions,decoupling capacitors have been mounted externally to the part on aboard, or mounted on a handler during testing, in order to ensure acleaner voltage supply to the part. However, for best decoupling, acapacitor must be mounted as close to the part as possible. But in aneffort to mount a capacitor close to a part, other drawbacks usuallyarise. For example, a capacitor can be embodied on a die, but this takesup valuable and limited die space. Also, when testing a part in ahandler, it is difficult to mount a capacitor close enough to the partto provide a reasonable amount of decoupling.

Thus, in an attempt to provide power supply decoupling, and also toimprove heat dissipation and electrical performance, it has been knownto use a multilayer lead frame wherein one of power supply and groundconnections is supplied through a first layer, and the other of powersupply and ground connections is supplied through a second layer. Forexample, U.S. Pat. No. 4,891,687 issued to Mallik et al. on Jan. 2,1990, discloses a multilayer IC package. However, this disclosurerequires the use of two conductive plates overlaying each other forpower and ground, respectively, and a separate lead frame overlaying theplates for wire bonding. As such, the solution is undesirably complex.Namely, two separate layers of adhesive must bond the two plates andlead frame, one plate must have a center portion punched out forplacement of the die and for wire bonding the die with the plates, andspecial tabs must be placed in precise locations on the plates forelectrically connecting the plates with lead fingers of the lead frame.

Similarly, U.S. Pat. No. 4,965,654, issued to Karner et al. on Oct. 23,1990, discloses a semiconductor package with a ground plane. However, inthis case, the adaptation is only for a Lead Over Chip (LOC)implementation, and there are not two separate plates for power supplyand ground connections, but rather only a ground plane and a lead frameoverlaying the ground plane. Consequently, the decoupling capacitiveeffect is not as complete. Furthermore, the ground plane is actually twoseparate plates overlaying the die and proximate the bonding pads. Thisis necessary in order to allow for wire bonding of the lead fingers withthe centrally located pads on the die. Moreover, the ground plane hasspecial, small, cut-away portions on a surface for wire bonding with thedie.

Given the foregoing problems associated with existing art andtechniques, objects of the present invention are to provide asemiconductor lead package system that provides good decoupling of apower supply to a semiconductor die with a simplified multilayer leadframe.

BRIEF SUMMARY OF THE INVENTION

According to principles of the present invention in its preferredembodiment, a multilayer lead frame for decoupling a power supply to asemiconductor die includes overlaying first and second lead frame bodieshaving an insulator disposed therebetween and at least one main leadfinger extending from each body. The bodies act as a capacitor todecouple the power supply to the die. One of the bodies and a respectivefinger provides one of power supply and ground connections for wirebonding with the die, and the other of the bodies provides the other ofpower supply and ground connections for wire bonding with the die.

According to further principles of the present invention, the first bodyincludes a die paddle for supporting the die, and the second bodyincludes a plate. The paddle overlays the plate with the insulatordisposed in between the paddle and plate, thereby providing anelectrical decoupling effect therebetween upon supplying power andground connections respectively.

According to further principles of the present invention, a method ofdecoupling a power supply is disclosed for a semiconductor die using amultilayer lead frame as disclosed herein. The method comprises thesteps of (1) supplying one of a power signal and a ground connection tothe die through the first main lead finger extending from one of thepaddle and plate, and wherein a wire bond communicates between the firstmain lead finger and one of a power and ground terminals of the die, and(2) supplying the other of the power signal and ground connection to thedie through the second main lead finger extending from the other of thepaddle and plate, and wherein a wire bond communicates between thesecond main lead finger and the other of the power and ground terminalsof the die.

The aforementioned principles of the present invention provide animproved multilayer lead frame for decoupling a power supply to asemiconductor die. Other objects, advantages, and capabilities of thepresent invention will become more apparent as the description proceeds.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view of an exploded representation of oneembodiment of the present invention showing the spacial relationshipbetween an IC chip and the present invention multilayer lead frame.

FIG. 2 is a plan view of an alternate embodiment of the presentinvention multilayer lead frame.

FIG. 3 is a cross-section view of a packaged IC device embodying themultilayer lead frame of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of an exploded representation of oneembodiment of the present invention showing the spacial relationshipbetween an IC chip (die) 10 and the present invention multilayer leadframe 20. Lead frame 20 comprises first conducting lead frame body 25having a die paddle 30 for supporting the die, and at least one firstmain lead finger 35 communicating with the paddle. Lead frame 20 furthercomprises a second conducting lead frame body 40 having a plate 45 andat least one second main lead finger 50 communicating with the plate. Inthe preferred embodiment, each main lead finger 35 and 50 is formed as apart of the paddle and plate, respectively, extending therefrom. Paddle30 overlays plate 45 (or it could be said plate 45 overlays paddle 30),and insulator 55 is disposed therebetween.

One of paddle 30 and plate 45, and respective main lead finger 35 and50, provides one of power supply and ground connections for wire bondingwith one of power and ground terminals 85 and 90 of die 10. The other ofthe paddle and plate, and respective communicating main lead finger,provides the other of power supply and ground connections for wirebonding with the respective power and ground terminals 85 and 90 of thedie.

Die 10 is supportable on a first planar surface 60 of paddle 30, and asecond planar surface 65 (not visible) of the paddle, opposite the firstplanar surface, overlays plate 45 with insulator 55 disposedtherebetween.

In its preferred embodiment, paddle 30 is of a shape and dimensionsubstantially similar to die 10. Namely, a circumferential dimension ofpaddle 30 is of a dimension substantially similar to a circumferentialdimension of die 10. Likewise, plate 45 and insulator 55 are of a shapeand dimension substantially similar to paddle 30.

Also in its preferred embodiment, insulator 55 is a double-sidedthermosetting or thermoplastic adhesive coated polyimide film (tape),such as that sold under the trade name duPont Kapton®, or a sprayed-onpolyimide or other highly dielectric material. Insulator 55 adherespaddle 30 to plate 45 and protects them from electrically shorting witheach other.

First body 25 further includes, optionally, one or more signal leadfingers 70, each having a tip disposed proximate to and separate frompaddle 30 for wire bonding signal leads with bonding pads (terminals) 80of die 10. Likewise, second body 40 further includes, optionally, one ormore signal lead fingers 75, each also having a tip disposed proximateto and separate from plate 45 for wire bonding signal leads withterminals 80 of die 10. Signal lead fingers 70 and 75 are termed“optional” because either first body 25 or second body 40 may havesignal lead fingers in a mutually exclusive manner, or both may havesignal lead fingers concurrently in any manner deemed best suited for aparticular die used in conjunction with the lead frame. See FIG. 2 forfurther alternate embodiment details.

It should be noted here that lead finger bar supports 95 are notpertinent to the invention other than for supporting the lead fingers aspart of the lead frame prior to being clipped off upon encapsulation ofthe die as is well known in the art. Also, although not shown in thedrawing, it is understood by those of ordinary skill in the art that aninsulator may be disposed between paddle 30 and die 10 as appropriate,depending on the type of die being used.

In reference to an example for this embodiment of the invention, assumefirst main lead finger 35 of paddle 30 is designated to receive a powersupply, and terminal 85 of die 10 is designated as a power supplyterminal. Assume also that second main lead finger 50 of plate 45 isdesignated as a ground connection finger, and terminal 90 is a groundconnection terminal for die 10. In this example, first main lead finger35 would be wire bonded to power terminal 85 of die 10, and second mainlead finger 50 would be wire bonded to ground terminal 90 of die 10. Anyother signal connections are properly wire bonded between terminals 80of die 10 and lead fingers 70 and 75 of either lead frame body,respectively. This configuration allows the paddle and plate to act as acapacitor to decouple the power supply to the die, ensuring a more cleanand stable voltage signal supply to the die.

This example configuration also demonstrates the simplicity of thepresent invention in providing a clean power supply to a die. Namely,(1) a separate lead frame does not overlay the paddle and plate for wirebonding as in the prior art; (2) no special punched out portions need tobe created in the paddle or plate for placement of the die as in theprior art; (3) no special tabs need to be placed in precise locations onthe paddle and plate for electrically connecting such with lead fingersof the lead frame as in the prior art; and (4) no special notchedportions need to be placed on the paddle and plate for wire bonding withthe lead fingers as in the prior art.

Referring now to FIG. 2, a plan view of an alternate embodiment of thepresent invention multilayer lead frame is depicted. Although shownseparately in this drawing, first lead frame body 102 includes paddle105 which overlays plate 110 of second lead frame body 112 according toprinciples of the present invention, and an insulator is disposedtherebetween (not shown). First main lead finger 115 extends from paddle105 for supplying one of power and ground connections, and second mainlead finger 120 extends from plate 110 for supplying the other of powerand ground connections. In this embodiment, all of the signal leadfingers 125 are disposed proximate to paddle 105 as part of first leadframe body 102, rather than some being disposed proximate to plate 110as part of second body 112.

Although FIGS. 1 and 2 depict two examples of how the paddle and plateare shaped, and how and where the main lead fingers could extend fromthe paddle and plate, and how and where the signal lead fingers could bedisposed proximate to the paddle and plate, it is obvious that anynumber of shapes and configurations could be used, and any number oflead fingers could be employed, in coordination with the die that is tobe wire bonded with the lead frame. For example, in FIG. 2, main leadfingers 115 and 120 could connect at any location around the peripheryof the respective paddle and plate 105 and 110. Specifically, thelocation of one of signal lead fingers 125 could be designated as thelocation for the connection of main lead finger 115. Likewise, body 102is currently referenced with paddle 105 for supporting the die andoverlaying plate 110, and body 112 is referenced with plate 110.However, if body 112 were to overlay body 102, then reference 110 wouldbe considered the paddle for supporting the die, and reference 105 wouldbe considered the plate.

FIG. 3 is a cross-section view of a packaged IC device 130 embodying themultilayer lead frame of the present invention. Die paddle 135 supportsdie 140 and overlays plate 145 with insulator 150 disposed therebetween.

One of paddle 135 and plate 145 provides one of power supply and groundconnections for wire bonding with one of power and ground terminals ofdie 140. The other of the paddle and plate provides the other of powersupply and ground connections for wire bonding with the respective powerand ground terminals of the die.

Wire bonds 155 and 157 communicate between terminals 160 and 165 of die140 and main lead fingers 170 and 175, respectively. Although notdistinguishable from this view, one of terminals 160 and 165 may be apower terminal, and the other may be a ground terminal. Likewise,although not distinguishable from this view, one of lead fingers 170 and175 may provide the power supply, and the other may provide the groundconnection for die 140. Signal lead fingers which are disposed onlyproximate the paddle and plate for wire bonding are not visible fromthis view as they are disposed “behind” main lead fingers 170 and 175.

Die 140 is supportable on a first planar surface 180 of paddle 135, anda second planar surface 185, opposite the first planar surface of thepaddle, overlays plate 145 with insulator 150 disposed therebetween.Insulator 150 adheres paddle 135 to plate 145 and protects them fromelectrically shorting with each other.

While a preferred embodiment of the invention has been disclosed,various modes of carrying out the principles disclosed herein arecontemplated as being within the scope of the following claims.Therefore, it is understood that the scope of the invention is not to belimited except as otherwise set forth in the claims.

What is claimed is:
 1. A multilayer lead frame and a semiconductor diecomprising: a first conducting lead frame body including a die paddlefor supporting a semiconductor die, said die paddle having a perimeter,at least one first main lead finger depending from said die paddle, afirst lead finger bar depending solely from said at least one first mainlead finger supporting a first plurality of lead fingers extending fromsaid first lead finger bar adjacent a first portion of said perimeter ofsaid die paddle; a second conducting lead frame body including a plateand at least one second main lead finger depending from said plate; atleast one additional lead frame segment including one lead finger barsupporting an additional plurality of lead fingers, the lead fingers ofeach said at least one additional lead finger segment extending from thefirst main lead finger bar to adjacent one of said die paddle and saidplate; an insulating material disposed between and substantiallytouching said die paddle and said plate, said insulating material beingselected from a group consisting of a polyimide and an adhesive tape;and a semiconductor die attached to said die paddle having wire bonds tosaid at least one first and at least one second main lead fingers andsaid first and additional pluralities of lead fingers.
 2. The lead frameof claim 1, wherein said die paddle and said at least one first mainlead finger provide a power supply connection for wire bonding with saidsemiconductor die and said plate and said at least one second main leadfinger provide a ground supply connection for wire bonding with saidsemiconductor die.
 3. The lead frame of claim 2, wherein said at leastone first main lead finger, said first lead finger bar and said firstplurality of lead fingers are included as part of said die paddle. 4.The lead frame of claim 2, wherein said at least one second main leadfinger are included as part of said plate.
 5. The lead frame of claim 1,wherein said insulating material includes a dielectric material.
 6. Thelead frame of claim 1, wherein said at least one first main lead fingerand said at least one second main lead finger extend from said diepaddle and said plate, respectively, on opposite sides of saidperimeter.
 7. The lead frame of claim 1, wherein said plate and said diepaddle are substantially similar in size and shape to said semiconductordie for mounting thereon.
 8. A multilayer lead frame for decoupling apower supply to a semiconductor die attached thereto comprising: a firstlead frame segment including a first body having a perimeter, a firstmain lead finger depending from said first body, at least one first leadfinger bar depending solely from said first main lead finger andsupporting a first plurality of lead fingers extending from said atleast one first lead finger bar adjacent a first portion of saidperimeter; a second body; a second lead frame segment including at leastone second lead finger bar supporting a second plurality of lead fingersextending from said at least one second lead finger bar adjacent one ofsaid first body and said second body; a second main lead fingerdepending from said second body; an insulating material disposed incontact with said first body and said second body, said insulatingmaterial being selected from a group consisting of a polyimide and anadhesive tape; and a semiconductor die attached to said first bodyhaving wire bonds to said first and second pluralities of lead fingersand said first and second main lead fingers.
 9. The lead frame of claim8, wherein said first body and said first main lead finger provide apower supply connection for wire bonding with said semiconductor die andsaid second body and said second main lead finger provide a groundsupply connection for wire bonding with said semiconductor die.
 10. Thelead frame of claim 9, wherein said first main lead finger, said firstlead finger bar and said first plurality of lead fingers are formed aspart of said first body.
 11. The lead frame of claim 8, wherein saidinsulating material includes a dielectric material.
 12. The lead frameof claim 8, wherein said first main lead finger and said second mainlead finger extend from said first body and said second body,respectively, on opposite sides of said perimeter of said first body.13. The lead frame of claim 9, wherein said first body and said secondbody are substantially similar in size and shape to said semiconductordie.